Abstract: A furnace for providing a source of molten aluminum or other metal includes a main chamber and a sweat chamber, the floor of which constitutes a sweat hearth on which ingots or sows are placed. A division wall separates the sweat chamber from the main chamber, and this wall contains ports located at the level of sweat hearth for providing communication between the two chambers. Each chamber, moreover, contains its own set of burners and has a discharge stack leading away from it. Each stack in turn has a refractory damper in it. The burners within the main chamber maintain the bath in a molten condition, and when these burners are in operation, the damper in the stack leading from the main chamber is closed, while the damper in the stack leading from the sweat chamber is open. Thus, the hot gases flow through the ports in the division wall and thence through the sweat chamber to the stack leading from that chamber. The hot gases preheat the sows.